Currently, in an electric control system, mechanical switches such as a contactor and a relay are widely used to control connection and breaking of a load. However, because an arc chute of common arc extinguishing use only functions when an arc breaks and exits to a particular length, an arc chute of common arc extinguishing use has defects that an arc extinguishing effect is poor, when a load breaks, an arc is great, and as a result, a contactor may be easily burnt.
For the above reasons, the arc extinguishing devices used for the mechanical switch arc suppressing appeared. For example, Chinese Patent No. CN01201907.0, entitled “ELECTRONIC ARC EXTINGUISHER”, and Chinese Patent Application No. CN200910306608.6, entitled “PHOTOELECTRIC COUPLING BASED HYBRID AC CONTACTOR PASSIVE SWITCH DRIVE CONTROLLER”, disclose that by means of connecting a thyristor and a mechanical switch of a contactor in parallel, a power source is connected to a control coil of the contactor; before the mechanical switch of the contactor breaks, a drive signal controlling switch-on of the thyristor is provided; the control coil at the contactor powers off; when the mechanical switch is separated, the thyristor is switched on; discharge delay is performed by a filter capacitor of a power supply circuit; a drive signal disabling switch-on of the thyristor is delayed, and the thyristor cuts off, completing a non-arcing break process.
Because there is a period of uncertain delay from the control coil of the contactor losing power to the mechanical switch breaking, in order to make the thyristor cut-off after the mechanical switch breaks to ensure reliable arc extinguishment, the thyristor needs to be switched on for a relatively long period (usually above tens of milliseconds); arc extinguishment in the controlling manner of closing a control signal in delayed time after the mechanical switch breaks necessarily increases unnecessary redundant switch-on work time of the thyristor, and long switch-on work time of the thyristor causes a poor overload capacity and low reliability of an entire arc extinguishing apparatus.